Field of the Present Invention
The present invention relates to a method of controlling a fuel cell system.
Description of Related Art
A fuel cell, for example, may be a stack configured by stacking a plurality of cells, each of which is formed by sandwiching a solid polymer electrolyte membrane including a solid polymer ion exchange membrane or the like from both sides by an anode and a cathode and further clamping outer sides thereof by one pair of separators. This fuel cell generates power by supplying hydrogen gas as a fuel gas to the anode of each cell and supplying air containing oxygen as an oxidant gas to the cathode.
In addition, it is known that a fuel cell vehicle equipped with such a fuel cell improves fuel efficiency by performing idle stop (hereinafter referred to as “idle stop of a fuel cell system”) for temporarily stopping power generation in the fuel cell.
Incidentally, it is known that, in this type of fuel cell, at the stop of power generation of the fuel cell including the idle stop of the above-described fuel cell system, a so-called crossover in which hydrogen gas of the anode side remaining within the fuel cell is transmitted through the solid polymer electrolyte membrane and diffused into the cathode side and oxygen in the air of the cathode side is transmitted through the solid polymer electrolyte membrane and diffused into the anode side occurs. When the crossover occurs, a reaction gas electrochemically reacts in the vicinity of the solid polymer electrolyte membrane and the solid polymer electrolyte membrane is likely to be deteriorated. Because of this, when the power generation of the fuel cell is stopped, it is necessary to reduce an oxygen concentration by consuming oxygen remaining on the cathode side of the fuel cell and form a nitrogen-rich atmosphere.
For example, in Published Japanese Translation No. 2007-506243 of the PCT International Publication, there is disclosed a combustor configured to promote the reaction between a fuel (fuel gas) and oxygen (an oxidant gas), and a method of controlling the fuel cell system which supplies nitrogen gas after oxygen has been consumed by the combustor to the anode and the cathode of the fuel cell when the fuel cell system is stopped.
In addition, in Japanese Unexamined Patent Application, First Publication No. 2003-115317, there is disclosed a method of controlling a fuel cell system which re-circulates an exhaust gas exhausted from a cathode of a fuel cell using a compressor to supply the re-circulated exhaust gas to the cathode when power generation of the fuel cell is stopped, continues the power generation according to oxygen remaining in the exhaust gas, and stops the power generation when a power generation voltage is less than or equal to a predetermined value.